Conventional golf balls can be divided into two general groups: solid balls or wound balls. The difference in playing characteristics resulting from these different types of construction can be significant. Balls having a solid construction are popular with golfers because they provide durability and maximum distance. Solid balls are generally made with a solid core, usually made of a cross linked rubber, enclosed by a cover material. Typically, the solid core is made of polybutadiene crosslinked with zinc diacrylate and/or similar crosslinking agents. Solid cores may also contain a number of layers. The cover is generally an ionomeric material, such as SURLYN®, which is a tradename for a family of ionomer resins produced by E. I. DuPont de Nemours & Co. of Wilmington, Del. Covers may include one or more layers.
The combination of the solid core and ionomeric cover materials provide a ball that is durable and abrasion resistant. However, because these materials are rigid, solid balls can have a hard “feel” when struck with a club. Also, due to their construction, these balls tend to have a relatively lower spin rate and higher initial velocity, which can provide greater distance and increased accuracy off the tee but less control for greenside play.
Recently, manufacturers have investigated the use of alternative polymers, such as polyurethane, for use as golf ball covers. For example, U.S. Pat. No. 6,132,324, incorporated herein by reference, discloses a method of making a golf ball having a polyurethane cover. Polyurethanes have been recognized as useful materials for golf balls since about 1960. Polyurethane compositions are the product of a reaction between a curing agent and a polyurethane prepolymer, which is itself a product formed by a reaction between a polyahl and an isocyanate. As disclosed in U.S. Pat. No. 4,594,364 to Pawloski, et al., “polyahl” includes any organic compound having at least two active hydrogen moieties and an average molecular weight of at least 62. Illustrative of such active hydrogen moieties are —COOH, —OH, NH2, ═NH, —CONH2, —SH and —CONH—. Typical polyahls include polyols, polyamines, polyamides, polymercaptans, polyacids, and the like. The curing agents used previously are typically diamines or polyols. A catalyst is often employed to promote the reaction between the curing agent and the polyurethane prepolymer.
U.S. Pat. No. 4,123,061 discloses a trifunctional polyol, a tetrafunctional polyol, and a diamine curing agents. U.S. Pat. No. 5,334,673 discloses the use of thermosetting and thermoplastic polyurethanes for forming golf ball covers and, in particular, thermosetting polyurethane made from a composition of polyurethane prepolymer and a slow-reacting amine curing agent, and/or a difunctional glycol.
The first commercially successful polyurethane covered golf ball was the Titleist Professional ball, first released in 1993. Subsequently, the Titleist Pro-V1 ball was introduced successfully in 2000 with a solid resilient polybutadiene core, a hard ionomer casing and a polyurethane cover. The Pro-V1 ball provided both professional and amateur players with long distance off of drivers and control for greenside play.
There remains a need to incorporate a nonionomeric casing layer into a multilayer golf ball so that it will perform as well as a golf ball having an ionomer casing.